IMPROVED HIGH TEMPERATURE CHIP

Description

[0001] The present invention relates to a temperature sensor, in particular a high-temperature sensor comprising a substrate, at least one resistance structure and at least two connection contacts, wherein the connection contacts electrically contact the resistance structure.

[0002] Such temperature sensors are used in the automotive industry to measure the exhaust temperature and / or combustion temperature of engine gases. Measurements often need to be taken as close to the engine as possible. Therefore, such sensors must be able to withstand the high temperatures of the combustion gases. Temperature sensors with a planar resistance structure are known, for example, from DE 197 42 696 A1.

[0003] Several proposals have been made in the prior art for constructing such high-temperature-stable temperature sensors. For example, DE 10 2007 046 900 B4 proposes a sensor with a self-supporting cover as protection for a platinum resistor structure. DE 10 2009 007 940 B4 discloses another high-temperature sensor in which the substrate contains zirconium oxide. To prevent poisoning with ions that are harmful to the platinum film resistor structure, DE 10 2011 051 845 B4 proposes additionally applying sacrificial electrodes to the substrate.

[0004] A temperature sensor that is supposed to function even under frequent temperature changes is known from DE 10 2012 110 210 B4. However, the described temperature sensor begins to drift at high temperatures after prolonged exposure to corrosive gases, particularly in the exhaust stream of a combustion engine. In the case of the temperature sensor described in DE 10 2012 110 210 B4, the observed deviation can be attributed to the diffusion of foreign atoms, such as chromium, nickel, iron, and silicon, from the exhaust stream into the resistor structure.

[0005] The object of the invention is therefore to overcome the disadvantages of the prior art. In particular, a temperature sensor with low sensor drift is to be provided. The object of the invention is achieved by a temperature sensor, in particular a high-temperature sensor, comprising a coated substrate, wherein the substrate contains a zirconium oxide or a zirconium oxide ceramic, at least one resistor structure, and at least two connection contacts, wherein the connection contacts electrically contact the resistor structure, wherein the substrate is coated with an insulating layer, wherein the insulating layer contains a metal oxide layer, the resistor structure and the free areas of the insulating layer on which no resistor structure is arranged are coated at least partially with a ceramic intermediate layer for passivation, and a protective layer is arranged on the ceramic intermediate layer.wherein at least one opening is formed in the insulation layer, which at least partially exposes a surface of the substrate, wherein the at least one opening is designed such that at least one central segment is created in the insulation layer, wherein the edges of the central segment do not have a common end with the edges of the substrate, wherein the resistance structure and the ceramic intermediate layer applied thereto are located entirely on the central segment, wherein both the central segment and the at least one framing opening are covered with the protective layer, wherein the at least one opening is filled with the material of the protective layer.

[0006] According to the invention, the substrate comprises a zirconium oxide or a zirconium oxide ceramic. In examples of the invention, the substrate may also consist of or essentially consist of a zirconium oxide or a zirconium oxide ceramic. Also, in examples of the invention, the insulating layer may consist of or essentially consist of a metal oxide layer. In one example, the substrate consists of a zirconium oxide or a zirconium oxide ceramic, and the insulating layer consists of a metal oxide layer.

[0007] The term "opening" can be understood as a material recess in the insulation layer or at the edge of the insulation layer. The material recess can be round, oval, rectangular, trench-shaped, or slot-shaped, for example. The term "layer" can be understood as a flat layer or a substantially flat layer, whereby several layers can be arranged one above the other.

[0008] The stability of the high-temperature sensor is advantageously increased by forming at least one opening in the insulation layer, which at least partially exposes a surface of the substrate. In examples of the invention, a plurality of openings are formed in the insulation layer.

[0009] In state-of-the-art temperature sensors, the insulation layer can form a channel for the penetration of foreign atoms. The porosity of the metal oxide in the insulation layer may be the reason for this. The porous structure promotes the diffusion of foreign atoms. When the foreign atoms reach the resistance structure, for example, a platinum thin-film structure, they alloy with the platinum and change the electrical resistance of the platinum thin-film structure. This effect can be minimized or eliminated by introducing at least one opening.

[0010] The opening or openings in the insulation layer, which at least partially expose a surface of the substrate, form a region that has no metal oxide material and, depending on the design of the opening or openings, divides the insulation layer into individual, separate segments. The openings can be designed such that at least one central segment is created in the insulation layer, which is preferably arranged in the middle of the substrate. The openings are preferably contiguous and frame the central segment. The central segment has edges, wherein the edges of the central segment do not have a common end with the edges of the substrate. The resistor structure and the ceramic intermediate layer applied thereon for passivation are located entirely on the central element.Both the central segment with the resistor structure and the ceramic intermediate layer, as well as the surrounding opening, are covered with a protective layer, for example, a glass-ceramic protective layer. In the invention, the opening(s) is / are filled with the material of the protective layer. The opening filled with the material of the protective layer forms a diffusion barrier for foreign atoms from the edges of the insulation layer into the central segment.

[0011] In one example, the opening and / or openings are slit-shaped, wherein the slit width is preferably between 5 pm and 1 mm, preferably between 10 pm and 300 pm, particularly preferably between 20 pm and 100 pm.

[0012] The longitudinal extent of the slot-shaped opening may be formed parallel and / or perpendicular to the longitudinal extent of the substrate, and / or the longitudinal extent of a plurality of slot-shaped openings may be formed parallel to one another.

[0013] In one example, the opening and / or openings expose at least one side surface of the substrate. The term "side surface" in this context can be understood as an area on the side or edge of a flat surface of the substrate.

[0014] In one example, the opening and / or openings completely surround the resistor structure. In another example, the opening and / or another of the openings at least partially frames one of the two terminal contacts of the resistor structure.

[0015] In a further example, the zirconium oxide or the zirconium oxide in the zirconium oxide ceramic is stabilized with oxides of a trivalent and a pentavalent metal, and / or at least one electrode is arranged next to the resistance structure on the insulation layer at least on one connection contact, wherein the electrode or the electrodes is or are formed integrally with the resistance structure.

[0016] The stabilization of zirconium oxide or zirconium oxide in the zirconium oxide ceramic can be understood as a structural stabilization in which a specific crystal structure is stabilized. Yttrium oxide is particularly preferred as an oxide of a trivalent metal. Tantalum oxide and / or niobium oxide are particularly preferred as an oxide of a pentavalent metal. Suitable mixtures are known, for example, from EP 0 115 148 B1.

[0017] By stabilizing the crystal structure with trivalent and pentavalent metal oxides, the thermal expansion of the substrate can be matched to the thermal expansion of the intermediate layer and the noble metals of the resistor structure. This can prevent or reduce thermally induced stress in the resistor structure.

[0018] In one example, the insulation layer is an aluminum oxide layer.

[0019] In a further example, the ceramic intermediate layer has a thickness between 1 pm and 50 pm, preferably a thickness between 4 pm and 10 pm.

[0020] These thicknesses are chosen to allow for the placement of a cover layer and, if necessary, a lid on the intermediate layer without the intermediate layer, the cover layer, or the lid flaking due to different thermal expansion. In another example, the protective layer comprises a glass or a glass-ceramic and / or the lid is a ceramic plate.

[0021] The glass can also be used to attach the lid.

[0022] In one example, the resistor structure includes a platinum material or a platinum alloy, in particular a platinum-based alloy.

[0023] Platinum or platinum alloys are particularly suitable for the production of high-temperature sensors.

[0024] Furthermore, the invention proposes the use of a temperature sensor in an exhaust system for controlling and / or regulating an engine, in particular a motor vehicle engine.

[0025] The invention also proposes a method for producing a temperature sensor, in particular a high-temperature sensor, comprising: Providing and coating a substrate, wherein the substrate contains a zirconium oxide or a zirconium oxide ceramic, with an insulating layer and forming at least one opening in the insulating layer, which at least partially exposes a surface of the substrate, wherein the insulating layer contains a metal oxide layer; arranging a resistor structure and at least two connection contacts on the insulating layer, wherein the connection contacts electrically contact the resistor structure; coating the resistor structure and the free regions of the insulating layer, on which no resistor structure is arranged, at least partially with a ceramic intermediate layer; and arranging a protective layer and / or a cover on the ceramic intermediate layer.

[0026] In one example, forming the at least one opening in the insulation layer comprises the step of: photolithographically forming the opening and / or forming the opening by laser ablation.

[0027] Providing the substrate may include providing a substrate made of zirconium oxide stabilized with yttrium oxide and tantalum oxide. The substrate may have a thickness of 380 μm and an area of ​​50 x 50 mm2. The insulating layer may be an aluminum oxide layer and may be applied to the substrate using a physical vapor deposition (PVD) process. The layer may be porous and have a thickness of 2.4 μm.

[0028] To create the resistor structure, a platinum thin film with a temperature coefficient of 3850 ppm / K can first be applied over the entire surface of the insulation layer using a PVD process. The resistor structure and the connection contacts can then be produced using a photolithographic process.

[0029] The intermediate layer made of aluminum oxide can then be applied to a thickness of 8 pm, for example, using screen printing or the aerosol deposition method, ADM, sputtering, or PVD. The intermediate layer can cover the platinum structure and the areas of the insulation layer adjacent to the platinum structure. The contacts and the edge areas of the substrate can remain free and are not covered by the intermediate layer. The opening in the insulation layer can then be laser-milled into the insulation layer as a continuous trench or slot around the entire resistor structure and the connection contacts. For example, the width of the opening can be approximately 100 pm. During this type of laser ablation of the insulation layer, the substrate's surface can also be slightly ablated to ensure complete removal of the insulation layer.Additional openings can be made, for example, around the connection contacts.

[0030] After forming the opening(s), a protective layer of glass frit can be screen-printed and fired over the entire surface. The protective layer can cover the intermediate layer and the insulation layer and fill the opening(s) in the insulation layer. The terminal contacts can remain free of the protective layer material.

[0031] The cover, for example a hard cover made of zirconium oxide, which can be stabilized with yttrium oxide and tantalum oxide, can then be arranged on the protective layer with a thickness of 250 pm.

[0032] Finally, the resulting temperature sensors can be separated from the panel, and connecting wires can be connected to the connecting contacts. Further features and advantages of the invention will become apparent from the following description, in which preferred embodiments of the invention are explained using schematic drawings.

[0033] It shows: Figure 1 shows a schematic exploded view of a temperature sensor known from the prior art; Figure 2a shows a schematic plan view of an insulation layer with a resistance structure arranged thereon of a temperature sensor known from the prior art; Figures 2b - 2d show schematic plan views of insulation layers with openings and resistance structures arranged thereon according to embodiments of the invention; and Figures 3a and 3b show schematic sectional views through a substrate with an insulation layer with openings, a resistance structure, an intermediate layer, and a protective layer arranged thereon according to an embodiment of the invention.

[0034] The Figure 1shows a schematic exploded view of a temperature sensor known from the prior art. A meandering layered resistor structure 11 is electrically connected to two connection contacts 12, 13. The resistor structure 11 is framed on slightly more than two sides by two electrodes 14, 15.

[0035] A substrate 16 made of a stabilized zirconium oxide or a zirconium oxide ceramic is coated with an insulating layer 17 made of metal oxide, which ensures that the resistor structure 11 is not short-circuited by the zirconium oxide, which is conductive at high temperatures, and that a harmful interaction between the zirconium oxide and the resistor structure 11 is prevented.

[0036] The resistance structure 11 is provided on its side facing away from the substrate 16 with an intermediate layer 18 as a diffusion barrier, which in turn is covered with a protective layer 19 for passivation, which can consist of glass or a glass ceramic and is covered with a cover 20. According to Figure 1 A ceramic plate is applied to the protective layer 19 as a cover 20. The ceramic plate provides additional passivation and acts as a mechanical "shield" against abrasion by particles in the housing in which the actual temperature sensor is mounted.

[0037] In the Figure 1 In the temperature sensor shown, the connection contacts 12, 13 of the temperature sensor with connecting wires 21 and 22 are strain-relieved via connection pads 23 and 24 with a fixation 25 consisting of an electrically insulating fixation drop. This fixation 25 is made of high-purity glass or glass-ceramic.

[0038] In addition to the embodiment of the intermediate layer 18 as a diffusion barrier mentioned at the beginning, it should be noted that this is applied either in the thin-film process with a thickness in the range of 0.2 to 10 pm, preferably 5 pm, or in the thick-film process with a thickness in the range of 5 to 50 pm, preferably 15 pm.

[0039] The thickness of the connection pads 23, 24 on the resistor structure 11 is in the range of 10 to 50 pm, preferably 20 pm. The substrate 16 as a carrier has a thickness in the range of 0.1 mm to 1 mm, preferably 0.4 mm, particularly preferably 0.38 mm.

[0040] The connecting contacts 12 and 13 are each arranged on one side. However, it is also possible to arrange both connecting contacts 12 and 13 on opposite sides.

[0041] Figure 2ashows a schematic plan view of an insulation layer 17 with a resistor structure 11 arranged thereon of a temperature sensor known from the prior art. Figure 2a Insulation layer 17 and resistance structure 11 shown can be used, for example, in the Figure 1 The temperature sensor shown can be used. The insulation layer 17 shown has no openings.

[0042] The Figures 2b to 2d show schematic plan views of insulation layers 17 with openings 30, 30a-d and resistor structures 11 arranged thereon according to various embodiments of the invention. Figure 2bIn the embodiment shown, an opening 30 is formed in the insulation layer 17, which exposes a surface of the substrate. The opening 30 can be designed such that a central segment is created in the insulation layer 17, which is arranged in the middle of the substrate. The central segment has edges, wherein the edges of the central segment do not have a common end with the edges of the substrate. In the embodiment shown, the opening 30 is represented as a circumferential opening in the material of the insulation layer 17, which exposes a surface of the substrate. The edges of the substrate and the regions of the substrate surface adjacent to the edges are not covered by the insulation layer. In this case, the insulation layer 17 can first be applied completely to the surface of the substrate and then removed again in a circumferential edge region.

[0043] In the Figure 2cIn the embodiment shown, the opening 30 in the insulation layer 17 is slit-shaped and completely surrounds the resistor structure 11 and the connection contacts 12, 13. The slit width can, for example, be in a range from 10 pm to 1 mm.

[0044] In Figure 2d An embodiment is shown in which a plurality of slot-shaped openings 30, 30a-d are introduced into the material of the insulation layer 17 and form a plurality of segments in the insulation layer 17. In the embodiment shown, individual slot-shaped openings 30, 30a-d surround the connection contacts 12, 13 and the resistance structure 11.

[0045] The Figures 3a and 3bshow schematic sectional views through a substrate 16 with an insulating layer 17 arranged thereon with openings 30, a resistance structure 11, an intermediate layer 18, and a protective layer 19 according to an embodiment of the invention. In the embodiment shown, the material of the protective layer 19 completely fills the openings 17. The openings 17 filled with the material of the protective layer 19 form a diffusion barrier for foreign atoms from the edges of the insulating layer 17 into the central segment. In the area of ​​the connection contacts 12, 13, there is no protective layer 19, as in Figure 3b shown. In Figure 3b also shows the openings 30b and 30c, which partially enclose the connection contacts 12, 13, and the opening 30d, which is arranged between the connection contacts 12, 13. List of reference symbols

[0046] 11 Resistor structure 12, 13 Connection contact 14, 15 Electrode 16 Substrate 17 Insulation layer 18 Intermediate layer

Claims

1. A temperature sensor, in particular a high-temperature sensor, having a coated substrate (16), wherein the substrate (16) contains a zirconium oxide or a zirconium oxide ceramic, at least one resistance structure (11) and at least two connection contacts (12, 13), wherein the connection contacts (12, 13) electrically contact the resistance structure (11), wherein the substrate (16) is coated with an insulation layer (17), wherein the insulation layer (17) contains a metal oxide layer, the resistance structure (11) and the free areas of the insulation layer (17) on which no resistance structure (11) is arranged are at least regionally coated with a ceramic intermediate layer (18) for passivation purposes, and a protective layer (19) is arranged on the ceramic intermediate layer (18), characterized in that at least one opening (30, 30a-d) is formed in the insulation layer (17) and at least sectionally exposes a surface of the substrate (16), wherein the at least one opening (30, 30a-d) is designed in such a way as to provide for at least one central segment in the insulation layer (17), wherein the edges of the central segment have no common termination with the edges of the substrate (16), wherein the resistance structure (11) and the ceramic intermediate layer (18) applied thereto are located completely on the central segment, wherein both the central segment and the at least one framing opening (30, 30a-d) are covered by the protective layer, wherein the at least one opening (30, 30a-d)is filled with the material of the protective layer (19).

2. The temperature sensor according to claim 1, characterized in that a lid (20) is arranged on the protective layer (19).

3. The temperature sensor according to any one of the preceding claims, characterized in that the opening (30, 30a-d) and / or openings (30, 30a-d) is / are slotted in design, wherein the slot width preferably measures between 5 µm and 1 mm, preferably between 10 µm and 300 µm, especially preferably between 20 µm and 100 µm.

4. The temperature sensor according to claim 3, characterized in that the longitudinal extension of the slotted opening (30, 30a-d) is designed parallel and / or perpendicular to the longitudinal extension of the substrate (16), and / or wherein the longitudinal extension of a plurality of slotted openings (30, 30a-d) are parallel to each other in design.

5. The temperature sensor according to any one of the preceding claims, characterized in that the opening (30, 30a-d) and / or openings (30, 30a-d) expose(s) at least one lateral surface of the substrate (16).

6. The temperature sensor according to any one of the preceding claims, characterized in that the opening (30) and / or openings (30) completely envelop the resistance structure (11).

7. The temperature sensor according to any one of the preceding claims, characterized in that the opening (30a-d) and / or an additional opening of the openings (30a-d) partially frames at least one of the two connection contacts (12, 13) of the resistance structure (11).

8. The temperature sensor according to any one of the preceding claims, characterized in that the zirconium oxide or the zirconium oxide in the zirconium oxide ceramic is stabilized with oxides of a trivalent and a pentavalent metal, and / or at least one electrode (14, 15) next to the resistance structure (11) is arranged on the insulation layer (17) at least on one connection contact (12, 13), wherein the electrode (14, 15) or the electrodes (14, 15) is / are designed as one piece with the resistance structure (11).

9. The temperature sensor according to any one of the preceding claims, characterized in that the insulation layer (17) is an aluminum oxide layer.

10. The temperature sensor according to any one of the preceding claims, characterized in that the ceramic intermediate layer (18) has a thickness of between 1 µm and 50 µm, preferably a thickness of between 4 µm and 10 µm.

11. The temperature sensor according to any one of the preceding claims, characterized in that the protective layer (19) contains a glass or glass ceramic and / or the lid (20) is a ceramic tile.

12. The temperature sensor according to any one of the preceding claims, characterized in that the resistance structure (11) contains a platinum material or a platinum alloy, in particular a platinum-based alloy.